//
/*****************************************************************
**       Advanced Encryption Standard implementation in C.      **
**       By Niyaz PK                                            **
**       E-mail: niyazlife@gmail.com                            **
**       Downloaded from Website: www.hoozi.com                 **
******************************************************************
This is the source code for encryption using the latest AES algorithm.
AES algorithm is also called Rijndael algorithm. AES algorithm is 
recommended for non-classified use by the National Institute of Standards 
and Technology (NIST), USA. Now-a-days AES is being used for almost 
all encryption applications all around the world.

For the complete description of the algorithm, see:
http://www.csrc.nist.gov/publications/fips/fips197/fips-197.pdf

Find the Wikipedia page of AES at:
http://en.wikipedia.org/wiki/Advanced_Encryption_Standard
*****************************************************************/


/***********************************************************/
/* THE CODE IN THIS FILE IS SET FOR 128-BIT ENCRYPTION ONLY */
/***********************************************************/

#include <string.h>

// The number of columns comprising a state in AES. This is a constant in AES. Value=4
#define Nb 4
// xtime is a macro that finds the product of {02} and the argument to xtime modulo {1b}  
#define xtime(x) ((x<<1) ^ (((x>>7) & 1) * 0x1b))
// Multiplty is a macro used to multiply numbers in the field GF(2^8)
#define Multiply(x,y) (((y & 1) * x) ^ ((y>>1 & 1) * xtime(x)) ^ ((y>>2 & 1) * xtime(xtime(x))) ^ ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^ ((y>>4 & 1) * xtime(xtime(xtime(xtime(x))))))


int	getSBoxValue(int num)
{
	int	sbox[256] = {
		//0     1    2      3     4    5     6     7      8    9     A      B    C     D     E     F
		0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76, //0
		0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, //1
		0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15, //2
		0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, //3
		0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, //4
		0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, //5
		0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8, //6
		0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, //7
		0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73, //8
		0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, //9
		0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, //A
		0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08, //B
		0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, //C
		0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, //D
		0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, //E
		0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16 }; //F
	
	return(sbox[num]);
}


int	getSBoxInvert(int num)
{
	int	rsbox[256] ={ 
		0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb, 
		0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb, 
		0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e, 
		0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25, 
		0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92, 
		0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84, 
		0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06, 
		0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, 
		0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73, 
		0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e, 
		0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, 
		0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4, 
		0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f, 
		0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, 
		0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61, 
		0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d };
	
	return(rsbox[num]);
}


// This function produces Nb(Nr+1) round keys. The round keys are used in each round to encrypt the states. 
//NOTE: make sure Key array is zeroed before copying password
void	AES_KeyExpansion(int Nk, int Nr, unsigned char *RoundKey, unsigned char *Key)
{
	// The round constant word array, Rcon[i], contains the values given by 
	// x to th e power (i-1) being powers of x (x is denoted as {02}) in the field GF(28)
	// Note that i starts at 1, not 0).
	int		Rcon[255] = {
			0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 
			0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 
			0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 
			0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 
			0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 
			0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 
			0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 
			0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 
			0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 
			0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 
			0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 
			0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 
			0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 
			0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 
			0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 
			0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb  };
	int		i, j, getSBoxValue();
	unsigned char	temp[4], k;
	
	// The first round key is the key itself.
	for (i = 0; i < Nk; i++) {
		RoundKey[i * 4] = Key[i * 4];
		RoundKey[i * 4 + 1] = Key[i * 4 + 1];
		RoundKey[i * 4 + 2] = Key[i * 4 + 2];
		RoundKey[i * 4 + 3] = Key[i * 4 + 3];
	}
	
	// All other round keys are found from the previous round keys.
	while (i < (Nb * (Nr + 1))) {
	
		for (j = 0; j < 4; j++) {
			temp[j] = RoundKey[(i - 1) * 4 + j];
		}
		
		if (i % Nk == 0) {
			// This rotates the 4 bytes in a word to the left once.
			// [a0,a1,a2,a3] becomes [a1,a2,a3,a0]
			k = temp[0];
			temp[0] = temp[1];
			temp[1] = temp[2];
			temp[2] = temp[3];
			temp[3] = k;
			
			// This takes a four-byte input word and applies the S-box
			// to each of the four bytes to produce an output word.
			temp[0] = getSBoxValue(temp[0]);
			temp[1] = getSBoxValue(temp[1]);
			temp[2] = getSBoxValue(temp[2]);
			temp[3] = getSBoxValue(temp[3]);
			
			temp[0] = temp[0] ^ Rcon[i / Nk];
		} else if (Nk > 6 && i % Nk == 4) {
			// This takes a four-byte input word and applies the S-box
			// to each of the four bytes to produce an output word.
			temp[0] = getSBoxValue(temp[0]);
			temp[1] = getSBoxValue(temp[1]);
			temp[2] = getSBoxValue(temp[2]);
			temp[3] = getSBoxValue(temp[3]);
		}
		
		RoundKey[i * 4] = RoundKey[(i - Nk) * 4] ^ temp[0];
		RoundKey[i * 4 + 1] = RoundKey[(i - Nk) * 4 + 1] ^ temp[1];
		RoundKey[i * 4 + 2] = RoundKey[(i - Nk) * 4 + 2] ^ temp[2];
		RoundKey[i * 4 + 3] = RoundKey[(i - Nk) * 4 + 3] ^ temp[3];
		
		i++;
	}
	
	return;
}


// This function adds the round key to state.
// The round key is added to the state by an XOR function.
void	AddRoundKey(int round, unsigned char state[][4], unsigned char *RoundKey) 
{
	int	i, j;
	
	for (i = 0;i < 4; i++) {
		for (j = 0;j < 4; j++) {
			state[j][i] ^= RoundKey[round * Nb * 4 + i * Nb + j];
		}
	}
	
	return;
}


// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
void	SubBytes(unsigned char state[][4])
{
	int	i, j, getSBoxValue();
	
	for (i = 0;i < 4; i++) {
		for (j = 0; j < 4; j++) {
			state[i][j] = getSBoxValue(state[i][j]);
		}
	}
	
	return;
}


void	InvSubBytes(unsigned char state[][4])
{
	int	i, j, getSBoxInvert();
	
	for (i = 0; i < 4; i++) {
		for (j = 0; j < 4; j++) {
			state[i][j] = getSBoxInvert(state[i][j]);
		}
	}
	
	return;
}


// The ShiftRows() function shifts the rows in the state to the left.
// Each row is shifted with different offset.
// Offset = Row number. So the first row is not shifted.
void	ShiftRows(unsigned char state[][4])
{
	unsigned char	temp;
	
	// Rotate first row 1 columns to left    
	temp = state[1][0];
	state[1][0] = state[1][1];
	state[1][1] = state[1][2];
	state[1][2] = state[1][3];
	state[1][3] = temp;
	
	// Rotate second row 2 columns to left    
	temp = state[2][0];
	state[2][0] = state[2][2];
	state[2][2] = temp;
	
	temp = state[2][1];
	state[2][1] = state[2][3];
	state[2][3] = temp;
	
	// Rotate third row 3 columns to left
	temp = state[3][0];
	state[3][0] = state[3][3];
	state[3][3] = state[3][2];
	state[3][2] = state[3][1];
	state[3][1] = temp;
	
	return;
}


void	InvShiftRows(unsigned char state[][4])
{
	unsigned char	temp;
	
	// Rotate first row 1 columns to right   
	temp = state[1][3];
	state[1][3] = state[1][2];
	state[1][2] = state[1][1];
	state[1][1] = state[1][0];
	state[1][0] = temp;
	
	// Rotate second row 2 columns to right   
	temp = state[2][0];
	state[2][0] = state[2][2];
	state[2][2] = temp;
	
	temp = state[2][1];
	state[2][1] = state[2][3];
	state[2][3] = temp;
	
	// Rotate third row 3 columns to right
	temp = state[3][0];
	state[3][0] = state[3][1];
	state[3][1] = state[3][2];
	state[3][2] = state[3][3];
	state[3][3] = temp;
	
	return;
}


// MixColumns function mixes the columns of the state matrix
// The method used may look complicated, but it is easy if you know the underlying theory.
// Refer the documents specified above.
void	MixColumns(unsigned char state[][4])
{
	int		i;
	unsigned char	Tmp, Tm, t;
	
	for (i = 0; i < 4; i++) {    
		t = state[0][i];
		Tmp = state[0][i] ^ state[1][i] ^ state[2][i] ^ state[3][i];
		Tm = state[0][i] ^ state[1][i];
		Tm = xtime(Tm);
		state[0][i] ^= Tm ^ Tmp;
		Tm = state[1][i] ^ state[2][i];
		Tm = xtime(Tm);
		state[1][i] ^= Tm ^ Tmp;
		Tm = state[2][i] ^ state[3][i];
		Tm = xtime(Tm);
		state[2][i] ^= Tm ^ Tmp;
		Tm = state[3][i] ^ t;
		Tm = xtime(Tm);
		state[3][i] ^= Tm ^ Tmp;
	}
	
	return;
}


// The method used to multiply may be difficult to understand.
// Please use the references to gain more information.
void	InvMixColumns(unsigned char state[][4])
{
	int		i;
	unsigned char	a, b, c, d;
	
	for (i = 0; i < 4; i++) {   		
		a = state[0][i];
		b = state[1][i];
		c = state[2][i];
		d = state[3][i];		
		state[0][i] = Multiply(a, 0x0e) ^ Multiply(b, 0x0b) ^ Multiply(c, 0x0d) ^ Multiply(d, 0x09);
		state[1][i] = Multiply(a, 0x09) ^ Multiply(b, 0x0e) ^ Multiply(c, 0x0b) ^ Multiply(d, 0x0d);
		state[2][i] = Multiply(a, 0x0d) ^ Multiply(b, 0x09) ^ Multiply(c, 0x0e) ^ Multiply(d, 0x0b);
		state[3][i] = Multiply(a, 0x0b) ^ Multiply(b, 0x0d) ^ Multiply(c, 0x09) ^ Multiply(d, 0x0e);
	}
	
	return;
}


// Cipher is the main function that encrypts the PlainText.
void	Cipher(int Nr, unsigned char *in, unsigned char *out, unsigned char state[][4], unsigned char *RoundKey)
{
	int	i, j, round = 0;
	void	AddRoundKey(), ShiftRows(), SubBytes(), MixColumns();
	
	//Copy the input PlainText to state array.
	for (i = 0; i < 4; i++) {
		for (j = 0; j < 4; j++) {
			state[j][i] = in[i * 4 + j];
		}
	}
	
	// Add the First round key to the state before starting the rounds.
	AddRoundKey(0, state, RoundKey); 
	
	// There will be Nr rounds.
	// The first Nr-1 rounds are identical.
	// These Nr-1 rounds are executed in the loop below.
	for (round = 1; round < Nr; round++) {
		SubBytes(state);
		ShiftRows(state);
		MixColumns(state);
		AddRoundKey(round, state, RoundKey);
	}
	
	// The last round is given below.
	// The MixColumns function is not here in the last round.
	SubBytes(state);
	ShiftRows(state);
	AddRoundKey(Nr, state, RoundKey);
	
	// The encryption process is over.
	// Copy the state array to output array.
	for (i = 0; i < 4; i++) {
		for (j = 0; j < 4; j++) {
			out[i * 4 + j] = state[j][i];
		}
	}
	
	return;
}


// InvCipher is the main function that decrypts the CipherText.
void	InvCipher(int Nr, unsigned char *in, unsigned char *out, unsigned char state[][4], unsigned char *RoundKey)
{
	int	i, j, round = 0;
	void	AddRoundKey(), InvShiftRows(), InvSubBytes(), InvMixColumns();
	
	//Copy the input CipherText to state array.
	for (i = 0; i < 4; i++) {
		for (j = 0;j < 4; j++) {
			state[j][i] = in[i * 4 + j];
		}
	}
	
	// Add the First round key to the state before starting the rounds.
	AddRoundKey(Nr, state, RoundKey);
	
	// There will be Nr rounds.
	// The first Nr-1 rounds are identical.
	// These Nr-1 rounds are executed in the loop below.
	for (round = Nr - 1; round > 0; round--) {
		InvShiftRows(state);
		InvSubBytes(state);
		AddRoundKey(round, state, RoundKey);
		InvMixColumns(state);
	}
	
	// The last round is given below.
	// The MixColumns function is not here in the last round.
	InvShiftRows(state);
	InvSubBytes(state);
	AddRoundKey(0, state, RoundKey);
	
	// The decryption process is over.
	// Copy the state array to output array.
	for (i = 0; i < 4; i++) {
		for (j = 0; j < 4; j++) {
			out[i * 4 + j]=state[j][i];
		}
	}
	
	return;
}


// in is buffer to be encrypted (16 bytes)
// out is encrypted buffer (16 bytes)
void	AES_encrypt(unsigned char *in, unsigned char *out, char *password)
{
	int		Nr = 10; // The number of rounds in AES Cipher
	int		Nk = 4; // The number of 32 bit words in the key
	unsigned char	Key[16] = {0};
	unsigned char	state[4][4]; // the array that holds the intermediate results during encryption
	unsigned char	RoundKey[240]; // The array that stores the round keys
	void		AES_KeyExpansion(), Cipher();
	
	// password becomes the key (16 bytes, zero-padded if shorter, truncated if longer)
	strncpy((char *) Key, password, 16);
		
	// The KeyExpansion routine must be called before encryption.
	AES_KeyExpansion(Nk, Nr, RoundKey, Key);
	
	// The next function call encrypts the PlainText with the Key using AES algorithm.
	Cipher(Nr, in, out, state, RoundKey);
	
	return;
}

//Pass in expanded key externally - this is more efficient if encrypting multiple times with
//the same encryption key
void	AES_encryptWithKey(unsigned char *in, unsigned char *out, unsigned char *RoundKey)
{
	int		Nr = 10; // The number of rounds in AES Cipher
	int		Nk = 4; // The number of 32 bit words in the key
	unsigned char	state[4][4]; // the array that holds the intermediate results during encryption
	void		AES_KeyExpansion(), Cipher();
	
	// The next function call encrypts the PlainText with the Key using AES algorithm.
	Cipher(Nr, in, out, state, RoundKey);
	
	return;
}


// in is encrypted buffer (16 bytes)
// out is decrypted buffer (16 bytes)
void	AES_decrypt(unsigned char *in, unsigned char *out, char *password)
{
	int		Nr = 10; // The number of rounds in AES Cipher
	int		Nk = 4; // The number of 32 bit words in the key
	unsigned char	Key[16] = {0};
	unsigned char	state[4][4]; // the array that holds the intermediate results during encryption
	unsigned char	RoundKey[240]; // The array that stores the round keys
	void		AES_KeyExpansion(), InvCipher();

	// password becomes the key (16 bytes, zero-padded if shorter, truncated if longer)
	strncpy((char *) Key, password, 16);
	
	//The Key-Expansion routine must be called before the decryption routine.
	AES_KeyExpansion(Nk, Nr, RoundKey, Key);
	
	// The next function call decrypts the CipherText with the Key using AES algorithm.
	InvCipher(Nr, in, out, state, RoundKey);
	
	return;
}

//Pass in expanded key externally - this is more efficient if encrypting multiple times with
//the same encryption key
void	AES_decryptWithKey(unsigned char *in, unsigned char *out, unsigned char *RoundKey)
{
	int		Nr = 10; // The number of rounds in AES Cipher
	int		Nk = 4; // The number of 32 bit words in the key
	unsigned char	state[4][4]; // the array that holds the intermediate results during encryption
	void		AES_KeyExpansion(), InvCipher();
		
	// The next function call decrypts the CipherText with the Key using AES algorithm.
	InvCipher(Nr, in, out, state, RoundKey);
	
	return;
}


